High Pressure Processing (HPP) is non-thermal sterilization of liquid and solid food by the application of high pressure of the order 3000-8000 ATM. The process retains the foods quality of freshness and nutrient content such as vitamins. HPP of foods is of increasing interest because it permits microbial inactivation at low or moderate temperature with minimum degradation. Also, the energy required for compression with HPP is far less than that required in the thermal treatment process. HPP can be used not only for preservation but also for changing the physical and functional properties of foods, and can be applied to a large number of food products using batch or continuous treatment units. The adiabatic heating caused by the fluid compressing at high pressure can lead to significant temperature distribution throughout the treated food. The inaccurate evaluation of this temperature variation would lead to the incorrect scale up of the high pressure processing (HPP) units from laboratory size to industrial size. In this book, the effects of transient pressure and the temperature distribution of a non-adiabatic treatment chamber were analysed and studied using CFD.